Sean Foster, 19, was assaulted by a man as he waited at a bus stop on Oxford Street in the Brisbane suburb of Bulimba on Tuesday at about 9am.

The man, who was reportedly pulling down rainbow "Bulimba 4 Marriage Equality" flags at the time, is yet to be identified and Queensland Police are continuing their investigations, however Mr Foster's godfather took to social media on Wednesday to upload a photo of his bloodied face, allegedly taken after the altercation.

"So many warnings to Turnbull about what this postal vote could unleash. Now my godson Sean has been punched while sitting at his bus stop, for objecting when a man began ripping down rainbow banners and hurling verbal abuse," Mr Rudd posted to his 53,000 followers on Instagram.

Findings by the ABC's Vote Compass released on Wednesday show support for the Yes vote in Queensland is the lowest than any other state or territory. The five Australian electorates with the lowest support for same-sex marriage are all just outside of Brisbane.

Mr Foster is a musician and plays guitar for the indie rock band, Concrete Surfers. Mr Rudd tagged the band in his social media post.

The quartet, according to triple J are "raising the ears of skate rock lovers across Australia", and are set to release a new single in the coming days.

Fairfax Media has approached Mr Foster and his management for comment.